Clamp device for clamping the trailing end portion of a sheet to the cylinder

ABSTRACT

A device comprising clamp means for clamping the trailing end portion of a sheet to one wall surface of a cutout formed in the cylinder after the leading end portion of the sheet is gripped by a portion of the peripheral surface of the cylinder whereby the trailing end portion of the sheet can be clamped to the cylinder.

United States Patent [1 1 Murata Oct. 8, 1974 CLAMP DEVICE FOR CLAMPING THE TRAILING END PORTION OF A SHEET TO THE CYLINDER [75] Inventor: Keisuke Murata, Tokyo, Japan [73] Assignee: Ricoh Co., Ltd., Tokyo, Japan [22] Filed: Apr. 19, 1973 [21] Appl. No.: 352,680

[30] Foreign Application Priority Data Apr. 28, 1972 Japan 4742734 [52] US. Cl. 101/407 A, 101/415.1 [51] Int. Cl. B411 21/00 [58] Field ofSearch 10l/415.l, 131.5, 125,

101/126,13l,l31.5,l32,132.5, 133, 378, 407-412, 246; 271/79, 82

[56] References Cited UNITED STATES PATENTS 3,203,074 8/1965 Monaghan l0l/4l5.1 X

3,375,781 4/1968 Grimm et a1 101/4l5.1 X 3,427,965 2/1969 Turner l0l/4l5.l X 3,664,260 5/1972 Miller 10l/4l5.l

Primary Examiner-J. Reed Fisher Attorney, Agent, or Firm-Cooper, Dunham, Clark, Griffin & Moran [5 7] ABSTRACT A device comprising clamp means for clamping the trailing end portion of a sheet to one wall surface of a cutout formed in the cylinder after the leading end portion of the sheet is gripped by a portion of the peripheral surface of the cylinder whereby the trailing end portion of the sheet can be clamped to the cylinder 8 Claims, 10 Drawing Figures PATENTED BET 1974 SE51 1 0f 2 FIG.|

SHEEI 2 BF 2 PAIENTEDum 81974 FIG.3(1 Fl'G.3b

FlG.3c

FIG.5

v manually on the master 1 CLAMP DEVICE Eon CLAMPING THE TRAILING END PORTION or A sIIEET TO THE CYLINDER I BACKGROUND or THE INVENTION This invention relates to clamp devices, and more particularly it is concerned with a device for clamping the trailing end portion of a sheet, such as a master sheet or photosensitive sheet used for offset printing apparatus or electrophotographic copying apparatus,

the image of the master plate.

I-Ieretofore, it has been customary to have the leading end portion of the master plate gripped by master plate grip claws provided in a cutout formed in the master cylinder and leave the trailing end portion free when: the master plate is mounted on the master cylinderwhile the latter is rotating. As soon as the master plate is mounted on the rotating master cylinder, an etching roller is brought into engagement with the master cylinder to force the master plate against the periphery of the master cylinder. The trailing-end portion of the master plate is spaced apart from the, periphery of the master cylinder-except when the etching roller moves over the trailing end portion. As a result, the trailing end portion of the master plate is-inadvertently brought into contact with an ink roller which is in an inoperative position, in spite of the fact that the etching operation is being performed. This results in ink adhering'to non-image regions of the master plate, thereby soiling In order to obviate this disadvantage, proposals have been made to clamp the'trailing end portion of the sheet to the master plate. In one device of the prior art to clamp the trailing end portion of the master plate to the master cylinder, a plurality of openings are formed in the leading and trailing end portions of the master plate to receive therein locking claws provided in a cutout formed in thema'ster cylinder so as to clamp both the leading and trailing end portions of the master plate to the master cylinder. This device is inconvenient, however, because the master plate must be mounted cylinder after stopping the ro-' tation thereof. 7

On the other hand, duplicating apparatus have been developed in recent years in which an electrophotographic photosensitive sheet having a photoconductive material layer on its surface is mounted on a drum, exposed to an optical image of an original by means of an optical system, and developed by a suitable developing device so that a master plate can be prepared on the SUMMARY OF THE INVENTION An object of this invention is to provide a device for automatically. clamping the trailing end portion of a sheet to a cylinder or drum while the latter is rotating.

Another object of the invention is to provide a device for automatically clamping the trailing end portion of a sheet to a cylinder or drum while the latter is rotating, comprising flexing means for moving the trailing end portion of a sheet away from a cutout formed in the cylinder in preparation for clamping the trailing end portion of the sheet to the cylinder.

The invention permits a sheet to be mounted automatically on the cylinder and uniformly brought into intimate contact with the periphery of the cylinder without requiring manual attention.

BRIEF DESCRIPTION OF THE DRAWINGS planatioti of the manner in which the trailing end pordrum. The duplicating apparatus of the type described of the'prior art have the disadvantage of exposure of the photosensitive sheet to an optical image of an original not being carried out satisfactorily and portions of the image in the trailing end portion of the sheet becoming unclear, because the trailing end portion of the sheet is free to move.

tion of a sheet is clamped to the cylinder;

FIG. 4 is a side viewof the cam for driving the displacing roller and the and roller cooperating with the cam;

FIG.- 5 is a side view of the arm placing roller.

DESCRIPTION OF APREFERRED EMBODIMENT to an embodiment shown in the drawings in which the invention is applied to an offset printing apparatus. In

FIG. -1, a master cylinder 1 is rotatably supported .by a

shaft 2 connected to opposite side plates (not shown) of the printing apparatus for rotation in the direction of an arrow 3. Formed in the periphery'of the master cylinder 1 is a cutout 4 in which a plurality of plate grip claws 5 are arranged and pivotally supported at their bases by a shaft 6 which in turn is supported at opposite ends to opposite sides 7. (only one of such sides is shown) of the apparatus. I

The grip claws 5 are urged to pivot clockwise in FIG. 1 by the biasing force of a spring (not shown) and normally maintained in pressing engagement with a planar portion of the cutout 4. When a plate supply command is given to the master cylinder 1, the plate grip claws 5 are moved to a phantom line position so as to grip a master plate 8 when the latter is supplied. The plate grip device constructed as aforementioned is known,

The device provided by the invention comprises a hold-down roller 11 and a flexing roller '12 disposed near the periphery of the master cylinderl and norspring 18 connected at one end to an immovable memsupporting the disber 16 and at the other end to a pin 17 planted on one of the arms 14.

The flexing roller 12 is rotatably supported by a shaft 21 supported at opposite ends by a pair of arms 22 shown in phantom line positions. The arms 22 are pivotally supported by a shaft 23 supported by the opposite side walls. The flexing roller 12 is made of a material which has a higher coefficient of friction than the material for the master cylinder 1 relative to the master plate 8.

Secured to the shafts 21 and 23 are pulleys 24 and 25 respectively over which an endless belt 26 is trained. Maintained in meshing engagement with a pinion 27 secured to one end of the shaft 23 is a sector gear 28 which is supported at its base by a shaft 29 connected to one of the opposite side plates. The sector gear 28 supports through a shaft a follower roller 31 which is juxtaposed to a cam 50 (See FIG. 4) secured, for example, to the shaft 2 supporting the master cylinder 1 and capable of sliding axially of the shaft 2. The sector gear 28 is adapted to make one pivotal movement in suitable timing when the cam 50 makes one complete revolution together with the master cylinder 1.

Follower rollers 52 and 53 (See FIG. are supported through shafts by the arms 14 and 22 supporting the hold-down roller 11 and flexing roller 12 respectively, and juxtaposed to drive cams (not shown) mounted on the shaft 2 supporting the master cylinder 1 for sliding movement axially of the shaft 2. The timing in which these cams are actuated is subsequently to be described. The arms 22 supporting the flexing roller 12 are urged to pivot counter clockwise about the shaft 23 by the biasing force of a compression spring 32 connected at one end to an immovable member (not shown) and at the other end to the free end of one of the arms 22.

The device according to the invention further comprises clamp means comprising a plurality of clamp members 34 each including a claw 34a at a free end thereof and disposed in the relatively large cutout 4 formed in the master cylinder, with the claws 34a being normally maintained in pressing engagement with a wall surface 33 of the cutout 4 opposite to the wall surface with which the grip claws 5 are maintained in engagement. More specifically, each claw 34a has secured to its underside a friction member 35 which is maintained in pressing engagement with the wall surface 33.

Each clamp member 34 is connected at its base by a screw 37 to a bent portion 36a of a slider 36 which is formed therein with slots 38 and 39 loosely receiving therein pins 41 and 42 respectively which are planted on one side of the master cylinder 1. Planted on the slider 36 is a pin 43 which is loosely received in a fork 44a formed at one end portion of a follower lever 44 which supports a roller 45 at the other end portion through a shaft. The follower lever 44 which is pivotally supported by a shaft 46 connected to one side of the master cylinder 1 is urged to pivot counter clockwise about the shaft 46 in FIG. 1 by the biasing force of a compression spring 48 connected at one end to a pin 47 planted on the master cylinder 1 and at the other end to the lever 44.

The roller 45 is juxtaposed to a cam (not shown) mounted, for example, on the shaft 2. When the roller 45 is brought into engagement with the cam, the follower lever 44 pivots clockwise about the shaft 46 in FIG. 1. The cam is moved to a position in which it is disposed in the path of movement of the roller 45 only when it is desired to cause the follower lever 44 to pivot or when the master plate is to be mounted on the master cylinder 1. Normally, the cam is spaced apart from the roller 45 or disposed in a position which is vertically spaced apart from the plane of FIG. 1.

As aforementioned, the hold-down roller 1 l and flexing roller 12 are disposed in the respective phantom line positions 11A and 12A when no master plate is mounted on the master cylinder 1. However, when the leading end portion of the master plate 8 is gripped by the grip claws 5 and move beneath the hold-down roller 11, the roller 11 is brought into pressing engagement with the periphery of the master cylinder 1 by the action of the cam so as to bring the master plate 8 into intimate contact with the periphery of the master cylinder 1.

As a rear end portion 8a (See FIG. 2) of the master plate 8 draws near the flexing roller 12 after the master cylinder 1 has substantially made one revolution, the roller 31 supported by the sector gear 28 and the roller 53 supported by one of the support arms 22 are actuated by the respective drive cams, so that the sector gear 28 pivots counter clockwise and the arms 22 supporting the roller 12 pivot clockwise. Thus the flexing roller 12 is brought into pressing engagement with the periphery of the master cylinder 1, and the pinion 27 and pulleys 25 and 24 are caused to rotate clockwise by the pivoting sector gear 28, thereby causing the flexing roller 12 to rotate in the same direction. Thus the flexing roller 12 rotates clockwise while the master cylinder l rotates counter clockwise as indicated by the arrow 3, so that portions of the peripheries of roller 12 and master cylinder 1 in contact with each other momentarily move in the same direction. The peripheral velocity of the roller 12 is about twice that of the master cylinder 1.

FIG. 2a shows the flexing roller 12 beginning to be brought into pressing engagement with the periphery of the master cylinder 1 as the trailing end portion 8a of the master plate 8 draws near the flexing roller 12. Since the flexing roller 12 rotates in a direction opposite to the direction of rotation of the master cylinder 1 and at a speed higher than that of the master cylinder, a portion of the master plate 8 is turned up in the direction of rotation of the cylinder 1 by the roller 12 on the periphery of the master cylinder 1 to form a flexed portion 51 as shown in FIG. 2b. By this action of the flexing roller 12, the trailing end portion 8a is moved upwardly from the cutout 4 to the periphery of the master cylinder 1. While the flexing roller 12 rotates, the master cylinder 1 rotates through about 40 in the direction of the arrow 3.

When the trailing end portion 8a is moved into engagement with the periphery of the master cylinder 1 as aforementioned, the roller 45 supported by the follower lever 44 (See FIG. 1) is pushed and moved outwardly by the cam, so that the slider 36 moves toward the cutout 4. That is, the claws 34a of the clamp members 34 disposed in the cutout 4 as shown in FIG. 2a are moved radially outwardly as shown in FIG. 2!).

As the claws 34a are beginning to move radially after the flexed portion 51 is formed in the master plate 8 by the flexing roller 12, the flexing roller 12 stops rotating. However, the master cylinder 1 continues to rotate in the direction of the arrow 3, so that the trailing end portion 8a is brought almost to a standstill by the frictional dragging of theflexing roller 12 on the master plate 8 and the flexed portion 51 is reduced in size, till the flexed portion 51 disappears and the master plate 8 is brought into intimate engagement with the master cylinder throughout its length as shown in FIG. 20. At this time, the trailing end portion 8a extends above the cutout 4.

At this time, the claws 34a reach the end of their radial movement and move into a position in which they are disposed above the trailing end portion 8a of the master plate 8 and disposed nearest the flexing roller 12. Then the claws 34a move downwardly into pressing engagement with the trailing end portion 8a so as to force the latter tightly over the wall surface 33, thereby clamping the trailing end portion 8a to the master cylinder 1. As soon as the claws 34a move downwardly to force the trailing end portion 8a against the wall surface 33, the hold-down roller 11 and flexing roller 12 are restored to the respective phantom line positions 11A and 12A.

Clamping the trailing end portion of the master plate to the master cylinder will be described with reference to FIG. 3. In FIG. 3a, the trailing end portion 8a of the master plate 8 extends above the clamp members 34 and prevents the upward movement of the claws 34a. The trailing end portion 8a is displaced in the direction of movement of the master cylinder by the flexing roller 12 to 'form the flexed portion 51 as shown in FIG. 3b. After the claws 34a have moved to the position shown in FIG. 3c, the trailing end portion 8a extends above the cutout 4 and beneath the claws 34a. Then the clamp members 34 are returned to their original position and the flexing roller 12 is moved to its phantom line position, whereby the trailing end portion 8a of the master plate 8 can be forced tightly over the wall surface as shown in FIG. 3d and clamped to the master cylinder 1.

What is claimed is:

1. A clamp device for clamping the trailing end portion of a sheet to the periphery of a cylinder provided with means for gripping the leading end portion of the sheet, comprising a sheet hold-down roller adapted to bring the sheet into pressing engagement with the periphery of the cylinder when the sheet is gripped at its leading end portion by the grip means and the sheet has moved beneath the hold-down roller, sheet flexing means disposed in the vicinity of said sheet hold-down roller and posterior thereto with respect to the direction of rotation of the cylinder and adapted to be brought into pressing engagement with the sheet as the trailing end portion of the sheet draws near the sheet flexing means so as to turn up a portion of the sheet in the direction of rotation of the cylinder and form a flexed portion in the sheet, clamp means provided in the cylinder and each including a free end portion adapted to move into and out of engagement with one wall surface of a cutout formed in the periphery of the cylinder, and means causing said clamp means to move outwardly away from the periphery of the cylinder when the trailing end portion of the sheet does not extend above the cutout after the flexed portion is formed in the sheet by the flexing means and causing the clamp means to move inwardly back to their original position when the trailing end portion of the sheet is disposed beneath the free ends of the clamp members whereby the trailing end portion of the sheet can be forced against said one wall surface of the cutout.

2. A device according to claim 1, wherein said clamp means comprises a plurality of clamp elements each having a free end positionable to press the trailing end portion of a sheet against said one wall surface of said cutout, and wherein said means causing said clamp means to move includes a member mounted on said cylinder for reciprocating motion in a direction generally radial of said cylinder and secured to said clamp elements, and means for reciprocating said lastmentioned member to cause successive outward and inward movement of said clamp elements.

3. A device according to claim 1 wherein said sheet flexing means comprises a roller adapted to rotate in a direction opposite to the direction of rotation of the cylinder when the trailing end portion of the sheet draws near the flexing means, so that portions of the peripheries of the roller and the cylinder in contact with each other momentarily move in the same direction, said roller having a peripheral velocity higher than the peripheral velocity of the cylinder.

4. A device according to claim 3, wherein said sheet flexing means further includes means for moving said last-mentioned roller into and out of a position for pressing a sheet against the periphery of said cylinder, and means for rotating said last-mentioned roller in a direction opposite to the direction of rotation of said cylinder in synchronism with movement of said roller into sheet-pressing position by said moving means, such that rotation of said last-mentioned roller in said opposite direction begins upon movement of said lastmentioned roller into sheet-pressing position and terminates prior to movement of said last-mentioned roller out of sheet-pressing position.

5. A device according to claim 2, wherein said means for rotating said last-mentioned roller includes a cam rotated with said cylinder and cam follower means for imparting to said last-mentioned roller a predetermined extent of angular displacement in correspondence with rotation of said cam.

6. A device according-to claim 2, wherein said means for moving said last-mentioned roller includes a pair of arms rotatably supporting said last-mentioned roller and pivotable about an axis fixed in relation to the axis of rotation of said cylinder.

7. A device according to claim 2, further including means for moving said sheet hold-down roller into and out of a position for pressing a sheet against the periphery of said cylinder.

8. A device according to claim 4, wherein said means for moving said sheet hold-down roller includes a pair of arms rotatably supporting said sheet hold-down roller and pivotable about an axis fixed in relation to the axis of rotation of said cylinder. 

1. A clamp device for clamping the trailing end portion of a sheet to the periphery of a cylinder provided with means for gripping the leading end portion of the sheet, comprising a sheet hold-down roller adapted to bring the sheet into pressing engagement with the periphery of the cylinder when the sheet is gripped at its leading end portion by the grip means and the sheet has moved beneath the hold-down roller, sheet flexing means disposed in the vicinity of said sheet hold-down roller and posterior thereto with respect to the direction of rotation of the cylinder and adapted to be brought into pressing engagement with the sheet as the trailing end portion of the sheet draws near the sheet flexing means so as to turn up a portion of the sheet in the direction of rotation of the cylinder and form a flexed portion in the sheet, clamp means provided in the cylinder and each including a free end portion adapted to move into and out of engagement with one wall surface of a cutout formed in the periphery of the cylinder, and means causing said clamp means to move outwardly away from the periphery of the cylinder when the trailing end portion of the sheet does not extend above the cutout after the flexed portion is formed in the sheet by the flexing means and causing the clamp means to move inwardly back to their original position when the trailing end portion of the sheet is disposed beneath the free ends of the clamp members whereby the trailing end portion of the sheet can be forced against said one wall surface of the cutout.
 2. A device according to claim 1, wherein said clamp means comprises a plurality of clamp elements each having a free end positionable to press the trailing end portion of a sheet against said one wall surface of said cutout, and wherein said means causing said clamp means to move includes a member mounted on said cylinder for reciprocating motion in a direction generally radial of said cylinder and secured to said clamp elements, and means for reciprocating said last-mentioned member to cause successive outward and inward movement of said clamp elements.
 3. A device according to claim 1 wherein said sheet flexing means comprises a roller adapted to rotate in a direction opposite to the direction of rotation of the cylinder when the trailing end portion of the sheet draws near the flexing means, so that portions of the peripheries of the roller and the cylinder in contact with each other momentarily move in the same direction, said roller having a peripheral velocity higher than the peripheral velocity of the cylinder.
 4. A device according to claim 3, wherein said sheet flexing means further includes means for moving said last-mentioned roller into and out of a position for pressing a sheet against the periphery of said cylinder, and means for rotating said last-mentioned roller in a direction opposite to the direction of rotation of said cylinder in synchronism with movement of said roller into sheet-pressing position by said moving means, such that rotation of said last-mentioned roller in said opposite direction begins upon movement of said last-mentioned roller into sheet-pressing position and terminates prior to movement of said last-mentioned roller out of sheet-pressing position.
 5. A device according to claim 2, wherein said means for rotating said last-mentioned roller includes a cam rotated with said cylinder and cam follower means for imparting to said last-mentioned roller a predetermined extent of angular displacement in correspondence with rotation of said cam.
 6. A device according to claim 2, wherein said means for moving said last-mentioned roller Includes a pair of arms rotatably supporting said last-mentioned roller and pivotable about an axis fixed in relation to the axis of rotation of said cylinder.
 7. A device according to claim 2, further including means for moving said sheet hold-down roller into and out of a position for pressing a sheet against the periphery of said cylinder.
 8. A device according to claim 4, wherein said means for moving said sheet hold-down roller includes a pair of arms rotatably supporting said sheet hold-down roller and pivotable about an axis fixed in relation to the axis of rotation of said cylinder. 